Canon's compact rangefinder tele — 100mm f/3.5 in Leica Thread Mount, manual focus.
The Canon 100mm f/3.5 is a compact telephoto rangefinder lens made in Japan for the 39mm Leica screw thread. It comes from Canon's later-1950s rangefinder line, carrying the Canon name after the earlier Serenar 100mm lenses. It served Leica-thread and Canon rangefinder bodies as a small medium telephoto.
This is a manual-focus, rangefinder-coupled Leica Thread Mount lens with a 100mm focal length and a maximum aperture of f/3.5. The mount is the 39mm Leica screw thread (LTM / L39 / M39). Focus and aperture are set on the barrel by hand. Element count, weight and filter thread are omitted here because they are not verified from the gap data.
A 100mm gives comfortable reach for portraits, distant detail and compressed perspective, and this f/3.5 version keeps size and weight modest. Slower teles of this class are typically sharp across the frame when stopped down slightly and suit good-light shooting. It handles travel, portraits and general longer-lens work well.
Buying used, inspect for haze, fungus and balsam separation in the cemented groups. Check the coatings for cleaning marks and wear, look for oily aperture blades, and confirm the focus helicoid is smooth. Rangefinder-coupling accuracy matters at 100mm, so test it on a body. It adapts well to Leica M via M39-to-M and to mirrorless with M39-to-E, M39-to-Z or M39-to-RF adapters.